[Typescript SimpleEvents] Simple Cancelable Event

An event type that returns a (boolean | undefined) value allowing callback functions to cancel an action.

Class Information

export interface CancelableEvent {
    on(callback: ()=> boolean): number;
    off(handle: number): void;
    trigger(): boolean | undefined;
}

export class SimpleCancelableEvent extends BaseEvent<void, boolean> implements CancelableEvent {
    on= (callback: () => boolean): number => super.add(callback);
    off= (handle: number): void => super.remove(handle);
    trigger= (): boolean | undefined => super.getResult(undefined, false);
}

• on: adds a callback to the invoke list and returns its handle;
• off: removes a callback from the invoke list based on its handle;
• trigger: invokes all the callback in order; if there are no callback registered it will return undefined; if there is at least one callback it will return true if at least one callback returns true, or false otherwise;

Example Usage

the following test.ts compiled into test.js:

import { SimpleCancelableEvent } from "typescript-simpleevents";

class EventTest {
    readonly cancelAction = new SimpleCancelableEvent();

    doAction(index: number) {
       if (!this.cancelAction.trigger()) {
           console.log(`Action ${index}!`);
       }
    }
}

const test = new EventTest();
test.doAction(1);
const handle = test.cancelAction.on(() => true);
test.doAction(2);
test.cancelAction.off(handle);
test.doAction(3);

wil have the output:

> node test.js
Action 1!
Action 3!